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Matteo Lisi, Patrick Cavanagh; The infinite regression illusion reveals dissociation between perception and action. Journal of Vision 2014;14(10):1221. doi: https://doi.org/10.1167/14.10.1221.
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Many psychophysical studies showed that visual motion can influence the perceived location of stationary stimuli. A classical result is that a stationary aperture filled with a drifting grating appear to be displaced in the direction of motion (De Valois & De Valois, 1991). This illusion also affects the visuomotor system as saccades to static, drifting Gabor patches show landing positions shifted in the direction of motion (Kosovicheva, Wolfe, & Whitney, 2012; Schafer & Moore, 2007). In the present study we presented stimuli that combined motion within the aperture (internal motion) and motion of the aperture itself (external motion), with the direction of one motion vector orthogonal to the other, as in the infinite regress illusion of Tse and Hsieh (2006). This combination leads to a striking illusion where the perceived direction of the aperture is given by a nonlinear sum of the two motion vectors (Tse & Hsieh, 2006). We find that when the external motion is along a path tilted ~35Â° from the vertical, the orthogonal internal motion can make the path appear vertical. This creates a large offset between the perceived and the physical location of the aperture, up to twice the size of the aperture itself (8 times the sigma of the Gaussian envelope) at the two endpoints of the motion path. We measured both the perceptual and saccadic localization of brief flashes superimposed on the motion stimuli. Surprisingly, we found that saccades did not show the perceptual position shifts, but instead targeted the physical locations of the flashes. Overall, the data highlight a dramatic dissociation between action and perception and suggest that, unlike perception, the saccade system is able to isolate the external target motion and ignore the irrelevant internal motion.
Meeting abstract presented at VSS 2014
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